Large craniofacial skeletal defects or deficiencies significantly compromise patient's life and remain challenging to treat. Distraction osteogenesis (DO), a mechanically-induced endogenous bone-regeneration approach, has been used as a major treatment modality. Though reliable in bone regeneration, the current DO approach is inefficient because it relies mostly on mechanical stimulation, hence requiring a substantially prolonged treatment time with heightened risks of infection, appliance breakage, noncompliance, and treatment failures. Consistent with the current NIDCR's mission on tissue engineering and regenerative medicine, this project has an overall goal to augment jaw bone regeneration by using mechanical stimulation combined with autologous stem cell-based tissue engineering approaches. The hypothesis is that mandibular DO can be significantly accelerated by the introduction of autologous bone marrow-derived mesenchymal stem cells (BM-MSCs) through scaffolds before distraction and booster BM-MSC injections during the consolidation phase. Young pigs, closely relevant to young humans who constitute the population commonly receiving craniofacial DO treatments, will be used. The project will first establish baseline parameters in control animals using our validated pig mandibular DO model. Aim 1 studies will then determine two critical aspects of introducing cells to the DO site, i.e., the use of undifferentiated or osteogenic-differentiated BM-MSCs, and the inclusion or exclusion of bone marrow-derived endothelial progenitor cells (BM-EPCs). Both of these aspects are highly relevant to osteogenesis and angiogenesis needed for bone regeneration, but no study to date has concurrently evaluated them in a DO site. Bone regeneration following cell transplantation will be compared to the baseline parameters derived from the controls in order to identify the lead osteogenic promoting combination. Next, the project will determine whether booster injection of BM-MSCs during the consolidation phase further improves bone regeneration (Aim 2). Bone regeneration following initial cell transplantation together with booster injections will e compared to that only with initial cell transplantation. The effects of using autologous platelet-rich plasma (PRP) to carry BM-MSCs for injections will also be determined by comparing the DO sites with PRP included in the injections versus DO sites without PRP. The combined data from Aim 1 and 2 will be employed to create an optimal treatment scheme to be evaluated in an accelerated DO protocols with a faster distraction and a shorter consolidation (Aim 3). These studies will determine whether or not an optimized DO with autologous stem cell intervention can substantially shorten (by several weeks) the DO treatment time while achieving similar quality and quantity of bone regeneration, compared to regular DO without cell augmentation. Overall, this project has the potential to establish a new paradigm for the management of large craniofacial bone deficiencies or defects using distraction osteogenesis.